The invention relates to improvements in apparatus for adjusting the camshafts of internal combustion engines.
The purpose of a camshaft adjusting apparatus is to ensure an optimal variable valve control. This is accomplished by ensuring that the valve control phase angle can be adjusted continuously and in an accurately controlled manner. As a rule, such apparatus employ adjusters which are force-lockingly connected with and share the angular movements of the camshafts. An electronic control system is provided to transmit signals which initiate rotary movements of the camshaft. The signals which the control system transmits initiate a preliminary adjustment of the camshaft relative to the crankshaft of the combustion engine.
As a rule, a conventional camshaft adjuster receives motion from a hydraulic drive. The fluid is or can be oil, and the requisite oil pressure is generated by the circuit which serves to pressurize the lubricant for the combustion engine. A drawback of such procedure is that, during the engine start-up phase (this phase is critical as far as the generation of exhaust gases is concerned), the angular position of the camshaft relative to the crankshaft still departs from the desired or optimal position. The reason is that, at such time or stage, the lubricating system is yet to build up a fluid pressure which is necessary to ensure a satisfactory phase adjustment of the camshaft relative to the crankshaft. In other words, the hydraulic drive for the camshaft adjuster is yet to build up the necessary fluid pressure, i.e., the first or initial ignition of the engine takes place prior to accurate phase adjustment of the camshaft relative to the crankshaft. An undesirable side effect of such drawbacks of conventional apparatus is that the rotating camshaft at first turns the idling camshaft adjuster which entails the generation of noise that is readily perceivable by the operator and/or other occupant(s) of the motor vehicle.